The present invention relates to a ribbon cartridge for use with a typewriter, a printer or like printing apparatus.
A ribbon cartridge for such applications comprises a lower casing and an upper casing which is coupled over the lower casing, though not limited to this design. Ribbon is stored in the lower casing wound on a supply reel. Generally, such ribbons are classified into a fabric type in which a fabric ribbon bears ink, a one time or disposable type in which a film layer and an ink layer are formed one upon the other and, each time a character is printed out, ink in the corresponding area is removed, and a multi-strike type which allows its each area to be hammered a plurality of times. It is a usual practice to feed the ribbon from the supply reel to the outside of the ribbon cartridge through an outlet formed through the lower casing, introduce it again into the ribbon cartridge through an inlet also formed through the lower casing at a predetermined spacing from the outlet, and wind it on a take-up reel by way of a feed mechanism installed in the lower casing. Where the ribbon cartridge is mounted to an operative position in a printing apparatus, a serrated roller forming part of a feed mechanism is brought into driven connection with a motor of the apparatus. Driven by the motor, the serrated roller or feed roller cooperates with another serrated roller such that the ribbon is progressively removed from the supply reel and fed to the take-up reel through between the coactive rollers. Data are printed out on a sheet of paper carried on a platen by selecting desired ones of numerous type members carried on a type wheel or like type element and hammering the type members in succession onto the paper through a part of the ribbon which spans the outlet and inlet of the lower casing.
In a printing apparatus which uses this type of ribbon cartridge and prints out data using a length of ribbon stretched between the outlet and the inlet of the lower casing, it is generally desired that a proper magnitude of tension be imparted to the ribbon while the latter is fed in order to promote exact data reproduction. Ribbon cartridges are usually provided with a special tension mechanism which puts the ribbon under tension in the path of movement from the supply reel to the take-up reel. However, the intricate tension mechanism which is independent of the rest of the arrangement in the ribbon cartridge results disproportionate time and labor necessary for assembling the whole ribbon cartridge while increasing the number of component parts which has critical influence on cost.
It is a first object of the present invention to provide a ribbon cartridge which needs a minimum number of component parts, and has a structure easy to assemble and quite simple.
Meanwhile, the ribbon stretched between the outlet and inlet is pressed against and largedly redirected by those edge portions of the lower casing where the outlet and inlet are defined. The pressure under which the ribbon is urged against the edges is considerable in order that the ribbon may be stretched without any slack between the outlet and inlet. However, though the edges concerned are rounded, their friction with the ribbon is of a magnitude which is even objectionable for smooth feed of the ribbon.
It is a second object of the present invention to provide a ribbon cartridge which ensures smooth feed of a ribbon throughout a predetermined path.
In case where the ribbon cartridge houses the one time ribbon or the multi-strike ribbon, the operator has to frequently check an amount of the ribbon remaining on the supply reel; otherwise, the ribbon may possibly run out during a printing operation to cause interruption. With this in view, a ribbon end sensor mechanism is usually installed in a printing apparatus while a ribbon cartridge is formed with a slot through its lower casing which extends across ribbon thereinside. As a tail end portion of the ribbon moves past the slot, it is sensed by the sensor mechanism to interrupt a printing operation.
There is known a ribbon end sensor of electric conduction type having electrodes which will penetrate through the slot into contact with the back of ribbon within a ribbon cartridge when the latter is mounted on the printing apparatus. Ribbon applicable to this type of sensor carries a conductive member on its back adjacent to the tail end so that the conductive member sets up electric conduction between the electrodes as it moves past the slot entrained by the ribbon. Another known ribbon end sensor is of the photoelectric type which comprises a light emitting element and a light receiving element. When a ribbon cartridge is loaded in the printing apparatus, the light emitting and light receiving elements will project into the ribbon cartridge through the slot of the lower casing to face the ribbon from opposite sides. Ribbon applicable to this type of sensor has a tail end portion constituted by a light transmitting member such that the light transmitting member passes light from the light emitting element therethrough to the light receiving element as it moves past the slot.
If the electrodes of the electric conduction type ribbon end sensor are located to the front face of the ribbon which does not carry the conductive member, they will fail to contact the conductive member on the back face of the ribbon and, therefore, to sense the tail end of the ribbon. Accordingly, the slot in the lower casing must be dimensioned small enough to prevent the electrodes from being positioned to the front of the ribbon. In contrast, the photoelectric type ribbon end sensor needs a relatively large slot in order to accommodate the light emitting and light receiving members at opposite sides of the ribbon and ensure a sufficient space for the transmission of light from the light emitting element to the light receiving element. A compromise between these conflicting requirements has been selecting a ribbon cartridge each time which meets a specific type of ribbon end sensor mechanism employed.
It is a third object of the present invention to provide a ribbon cartridge which is applicable to both the electric conduction type and photoelectric type ribbon end sensor mechanisms.
Another known implement for checking a remaining length of ribbon is a window for confirmation by sight which is formed through the upper casing of the ribbon cartridge. This still involves a drawback that, since both the ribbon cartridge and ribbon bear the same color such as black and are hardly distinguishable from each other, the operator cannot confirm a length to go without interrupting the printing operation each time and checking through the window by sight.
It is a fourth object of the present invention to provide a ribbon cartridge which permits a remaining length of ribbon to be seen instantaneously and easily while a ribbon cartridge is in use.
It is another object of the present invention to provide a generally improved ribbon cartridge.